Where's it leaking from? Although that may not matter anymore. It sounds like it's slipping in addition to the hard shifts when cold.
Mine also shifts hard when it's cold, but it's on it's last legs.
Since you say you would need to replace the tranny to fix the leak, sounds like you will have to do that anyway. Do the torque converter and flush the cooling lines out as well.
If it's leaking from somewhere else that can be repaired inexpensively, then I would replace that and do a tranny drain and refill with Honda ATF. Drain/ refill, drive for a couple days, repeat. Three times total. If you try a drain and refill, note how much if any black crap is on the magnetic plug. Wipe it off and reinstall. If all else fails, try some Lucas or Tranny Rx.